1. Field of the Invention
The present invention relates generally to medical devices and, more particularly, to sensors used for sensing physiological parameters of a patient.
2. Description of the Related Art
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In the field of medicine, doctors often desire to monitor certain physiological characteristics of their patients. Accordingly, a wide variety of devices have been developed for monitoring many such physiological characteristics. Such devices provide doctors and other healthcare personnel with the information they need to provide the best possible healthcare for their patients. As a result, such monitoring devices have become an indispensable part of modem medicine.
One technique for monitoring certain physiological characteristics of a patient is commonly referred to as pulse oximetry, and the devices built based upon pulse oximetry techniques are commonly referred to as pulse oximeters. Pulse oximetry may be used to measure various blood flow characteristics, such as the blood-oxygen saturation of hemoglobin in arterial blood, the volume of individual blood pulsations supplying the tissue, and/or the rate of blood pulsations corresponding to each heartbeat of a patient. In fact, the “pulse” in pulse oximetry refers to the time varying amount of arterial blood in the tissue during each cardiac cycle.
Pulse oximeters typically utilize a non-invasive sensor that transmits light through a patient's tissue and that photoelectrically detects the absorption and/or scattering of the transmitted light in such tissue. One or more of the above physiological characteristics may then be calculated based upon the amount of light absorbed or scattered. More specifically, the light passed through the tissue is typically selected to be of one or more wavelengths that may be absorbed or scattered by the blood in an amount correlative to the amount of the blood constituent present in the blood. The amount of light absorbed and/or scattered may then be used to estimate the amount of blood constituent in the tissue using various algorithms.
Conventional pulse oximetry sensors are either disposable or reusable. Disposable sensors are typically simple bandage-type structures attached to the patient with adhesive materials, providing a contact between the patient's skin and the sensor components. However, their flexible nature renders them susceptible to motion artifacts caused by mechanical deformation of the sensor. Additionally, the adhesives used to secure the bandage sensors are generally designed for a single application, as they tend to lose adhesive strength when removed from the tissue for repositioning of the sensor. The sensor adhesives may also not adhere well to tissue that has blood or sweat on the surface.
Reusable sensors are often semi-rigid or rigid clip-type devices with three-dimensional geometry and moving parts. The clips generally affix the sensor components to a patient's tissue with spring-loaded hinges designed to hold the sensor in place after application. Clip-style pulse oximeter sensors are used repeatedly and, typically, on more than one patient. Therefore, over the life of the sensor, detritus and other bio-debris (sloughed off skin cells, dried fluids, dirt, and so forth) may accumulate on the surface of the sensor or in crevices and cavities of the sensor, after repeated uses. Thus, a thorough cleaning of a clip-style sensor may involve disassembly of the sensor and individual cleaning of the disassembled parts, or may involve careful cleaning using utensils capable of reaching into cavities or crevices of the sensor. Such cleaning is labor intensive and may be impractical in a typical hospital or clinic environment. Clip-style sensors with hinges or complex moving parts may also be more expensive to manufacture and transport. For example, a clip-style sensor with a complex structure and moving parts may require extra protection during shipping. Additionally, the complex structure of a clip-style sensor prevents easy stacking of multiple sensors in a single packaging system.
Although the clip-style sensor design provides a familiar and easy-to-use device for affixing the sensor components to a patient, the structure of the clip provides cleaning, manufacturing, and packaging challenges. It would be desirable to provide a clip-style pulse oximetry sensor that is easy to manufacture and use and that also provides suitable tissue contacting strength without complex mechanical components.